Modular type multi-stage interrupter with ionized gas assisting in breakdown and eventual arc extinction



Jan. 13, 1970 R. T. CASEY 3,489,872 MODULAR TYPE MULTI-STAGE INTERRUPTERWITH IONIZED GAS ASSISTING .IN BREAKDOWN AND E ARC EXTINCTION FiledSept.

VENTUAL 22. 1967 United States Patent US. Cl. 200144 9 Claims ABSTRACTOF THE DISCLOSURE A circuit interrupter having a first arc chamber inwhich an arc is generated by a moving contact and elongated upondiverging arc runners; the gases from the interruption are vented to theexternal air, but a small portion of the gases is also directed into asecond arc chamber having a pair of spaced electrodes connectedelectrically in parallel with the first contacts and having a secondpair of diverging arc runners; when the arc has been drawn and elongatedin the first chamber, creating a high voltage drop thereacross, thegases deflected to the second chamber cause breakdown between the secondelectrodes; the second arc is also elongated on diverging arc runnersand extinguished; each of the arc chambers is separately enclosed andforms a module such that one, two, three or more may be utilized,depending upon the voltage of the system involved.

BACKGROUND OF THE INVENTION Field of the Invention The present inventionrelates to electric circuit interrupters of the type utilizing contactsoperating in air or other dielectric gaseous media.

Description of the prior art.

Patent application No. 669,918 filed Sept. 22, 1967 by R. L. Hurtlediscloses an electric circuit breaker in which an arc is initiated in afirst chamber and then transferred to a second pair of electrodes inanother chamber for further elongation and final interruption. Patentapplication No. 669,900 filed Sept. 22, 1967 by H. G. Willard disclosesan improved form of such multi-stage interrupter in which the arc is notonly initiated in the first chamber, but is elongated to a high voltagecondition there and then its gases are used to trigger breakdown betweena parallel connected set of electrodes, permitting further elongationand voltage development. In the Willard application, no voltagegeneration occurs in the first arc chamber prior to triggering of thesecond arc chamber. Thus no voltage escalation of the arc is achieved.In the Hurtle application, venting of the first arc chamber is impeded.Moreover, a very specialized casing is required for its use, making itrelatively expens1ve.

OBJECTS OF THE INVENTION It is an object of the present invention toprovide a multi-stage interrupter of the general type shown in theaforementioned Willard and Hurtle applications which permits the firstunit as well as succeeding units to operate in their best manner withoutventing being impeded by the succeeding stage.

It is a further object of the invention to provide a multistageinterrupter of the type described in the aforesaid applicationsutilizing a plurality of assemblies of arc extinguishing units which mayall be substantially identical, and of the type used for single polecircuit breakers, thereby greatly facilitating manufacture and assembly,and reducing cost.

SUMMARY OF THE INVENTION In accordance with the invention in one form, amultistage circuit interrupter is provided including at least twoseparately enclosed arc interruption chambers. The first of thesechambers contains a movable contact movable to generate an electric arcand means for elongating the arc to develop a high voltage thereacross;the second chamber contains a pair of spaced electrodes connectedelectrically in parallel with the contacts of the first chamber,including diverging arc runner portions for elongating the arc. Thesecond arc chamber is positioned so that its electrodes at their closelyspaced point are adjacent the widely spaced portion of the first arcchamber but are laterally spaced therefrom. The major portion of the arcgases from the first chamber accordingly may be vented therefrom withoutrestriction. An insulating conduit of suitable refractory material leadsfrom a point adjacent the output of the first arc chamber to thecloselyspaced point of the electrodes of the second arc chamber, wherebya small portion of the hot arc gases emitted from the first arcinterrupting chamber are deflected into the space between the secondelectrodes, causing breakdown and transfer of the arc thereto.Electrical resistive devices, which may be of the positive temperaturecoefiicient of resistance type are preferably connected in seriesrelation in the line connecting the second electrodes in parallel withthe first elctrodes. The invention will be more fully understood fromthe following detailed description, and its scope will be set forth inthe appended claims.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a front elevation view ofan electric circuit breaker constructed in accordance with theinvention, portions of the top wall and insulating casing portionsthereof being broken away to show the interior construction;

FIGURE 2 is a side elevation view of a first arc chamber portion of thecircuit breaker of FIGURE 1, the side wall thereof nearest the observerbeing removed;

FIGURE 3 is a side elevation view of a second arc chamber portion of thecircuit breaker of FIGURE 1;

FIGURE 4 is a schematic diagram of the electric circuit connections ofthe circuit breaker of FIGURE 1, and

FIGURE 5 is a fragmentary view of a modified arc chamber interconnectingmeans for the circuit breaker of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawing, the invention isshown as incorporated in a multi-stage electric circuit breakercomprising three main sections 10, 11, and 12.

Section 10 comprises a generally rectangular casing including insulatingside walls 13 of suitable gas evolving material defining a first arcchamber 10A having supported therein a pair of terminal straps 14 and15. The straps 14 and 15 have stationary contacts 16 and 17 respectivelysupported on intermediate portions 14A, 15A thereof. The straps 14 and15 also include arc runner portions 14B, 15B diverging outwardly fromeach other and terminating in tip portions 14C, 15C. The are chamber 10Ais closed at the top by a bafile 18 of suitable material havingangularly diverging slot-like openings 19 therein to permit the exhaustof arc gases.

A movable contact member 20 is supported in the arc chamber 10A carryinga pair of movable contacts 22, 23, cooperating with the stationarycontacts 14A, 15A, respectively. A contact operating rod 20A is providedfor operation of the contact member 20 by suitable means, not shown. Itwill be understood that any desired operating mechanism may be utilizedto operate the movable contact member between open and closed circuitpositions, including if desired, means from moving the movable contactin either or both directions by solenoid action. In the formillustrated, a circuit breaker mechanism, not shown, is provided, whichmay be manually operated by means of the handle 24.

When the movable contact member 20 is moved from the closed position asshown in FIGURE 2 to the open position (i.e., downwardly as shown), apair of short arcs are drawn between the corresponding movable andstationary contacts. These short arcs quickly blend together to form asingle arc extending between the straps 14 and 15 at their narrowestpoint. This single arc is subsequently moved upwardly by action of thegases trapped in the contact chamber 138, and also by its own magneticblow-out action. The are moves outwardly along the runners 14B, 158 to afinal position between the tips 14C, 15C where it remains untilextinguished, it being understood that a large quantity of extremely hotgases generated by the are during its movement continue on and arevented through the openings 19.

The casing of the section 11 is substantially identical to that of thesection 10, with the opening which is provided in the section for thehandle 24 being closed by a closure plate 26. The arc chamber 11A of thesection 11 in the illustrated embodiment is identical to that describedabove in connection with section 10, excepting that the movable contactmember 20 and its operating rod 20A are omitted, and the opening for theoperating rod 20A is closed by a suitable closure plug of insulatingmaterial 27. Otherwise, similar numbers indicate similar parts.

An interconnecting conduit or pipe 29 of suitable refractory insulatingmaterial extends through aligned openings in the side walls of thechambers 10 and 11 and serves to interconnect the upper portion of thearc chamber 10A with the lower portion of the arc chamber 11A.Accordingly, when hot arc gases are generated in the arc chamber 10A,the greatest portion thereof are vented directly to the outer atmospherethrough the openings 19, but a small portion thereof is also led to thechamber 11A in the space between the electrodes 14 and thereof for apurpose to be described.

The third section 12 is identical to section 11 and is also connectedthereto by a similar interconnecting conduit 29A.

The conductive straps 14 and 15 of each of the sections 10, 11 and 12are connected electrically in parallel as indicated in the schematicdiagram of FIGURE 4, there being resistors 31, 32 connected between thesections 10A and 11A and the sections 11A and 12A respectively as shown.

OPERATION In operation, assuming the circuit breaker to be closed andconducting current, the primary current path, referring to FIGURE 4, isfrom incoming terminal 34 to the terminal strap 14 of the section 10 andstationary contact 14A and thence through the movable contacts andbridging contact member to the stationary contact 15A and its supportingstrap 15 to the outgoing terminal 35. When the movable contact member ismoved toward open position, a pair of short arcs are drawn between thstationary contacts 14A, 15A' and the corresponding movable contacts 22,23. These short arcs quickly bridge together t form a single areextending between the terminal straps 14 and 15. This are is movedupwardly by the force of gases generated in the portion 10A of the arcchamber 10A and also by its own magnetic action (which may besupplemented by magnetic blowout means if desired) until the arc reachesits final elongated condition at the ends 14C, 15C. The ionized gasesgenerated by the arc in its movement to its elongated condition are forthe most part blown out of the interrupting chamber 10A through thevent-openings 19. A small portion, however, are directed through theconduit 29 to the arc chamber 11A of the adjacent section 11.

Since there is a high voltage existing across the arc in its elongatedcondition, and since the terminal straps 14, 15 of the adjacent section11A are connected electrically in parallel, this voltage appears betweenthese electrodes of the adjacent chamber 11A. If the air in the spacebetween the straps 14, 15, of the chamber 11A were to maintain gooddielectric condition, no breakdown could occur therebetween. Because ofthe introduction of hot ionized gases through the conduit 29, however,the space between the electrodes 14, 15 in the chamber 11A becomesconductive, and breakdown occurs therethrough, the current then takingthe path from the terminal 34 through the interconnecting lead to theterminal strap 14 of the chamber 11A to the terminal strap 15 thereof,through the resistor 31 to the outgoing terminal 35. Since this pathby-passes the original arc position, the arc becomes extinguished in thechamber 11A, it being appreciated that the space in the chamber 11A hashad good dielectric restored by reason of the generation therein of highdielectric gases from the side walls thereof by the action of the arcand simultaneous expulsion of arc gases. Following initiation of the arcin the chamber 11A, the arc is moved out along the runners 14 and 15 toan elongated condition thereby further increasing the voltage droptherethrough. In accordance with a preferred form of the invention,resistors 31 and 32 are made of high positive temperature coefiicient ofresistance material, whereby after a short period of conducting currenttherethrough their resistance increases substantially because of theflow of current therethrough, further increasing the voltage drop.

In systems of medium voltage levels, such as 600 to 2000 volts, only thefirst two stages of the interrupter may be necessary. For highervoltages, however, a third stage may be used, such as illustrated atsection 12. A communicating conduit 29A is used to interconnect the arcchambere 11A with the arc chamber 12A so as to initiate breakdownbetween the electrodes 14 and 15 of the arc chamber 12A when the arc hasbeen developed to its longest length by the section 11. This causes thecircuit to take the path through the electrodes 14 and 15 of the arcchamber 12A and through both of the resistors 31 and 32 shown in FIGURE4. By this means the arc drop may be escalated to extremely high values,such for example as 5,000 to 10,000 or more volts.

The invention has been shown as utilizing three identical insulatingenclosures for the sections 10, 11 and 12 since this aifords convenienceand manufacturing advantages. It will be apparent, however, that theinsulating material required in the second and third sections may bereduced by utilizing a casing only just large enough to enclose therespective arc chambers.

Referring to FIGURE 5, another embodiment of the invention is disclosedin which an ionized-gas conduit or pipe 29' is utilized which has aright angle bend therein so as to receive are gases in the direction ofmain flow f r om the first arc chamber such as 10A and then direct thesegases sidewise to adjacent arc chamber such as 11A. This form has theadvantage of not requiring a hole through the side wall of the first arcchamber, since the conduit 29' may be positioned with its open endclosely adjacent one of the openings 19 of the arc baffle member 18,thereby requiring no modification of the basic circuit breaker 10.

While a specific embodiment of the invention has been shown, it will bereadily appreciated that many modifications thereof may be readily bemade and it is therefore intended by the appended claims to cover allsuch modifications as fall within the true spirit and scope of theinvention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A multi-stage electric circuit interrupter comprising:

(a) an insulating casing having at least first and second arc chamberstherein;

(b) separable contact means in said first arc chamber for drawing an arctherein;

(c) a pair of diverging arc runners in said first arc chamber havingclosely spaced end portions and widely spaced end portions forelongating said arc to increase the voltage drop therethrough;

(d) a pair of spaced electrodes in said second arc chamber saidelectrodes having diverging arc runner portions having closely spacedend portions and widely spaced end portions;

(e) means connecting said electrodes of said second arc chamberelectrically in parallel with said arc runners of said first arcchamber;

(f) conduit means extending between said first and sec- 0nd arc chambersfrom a position between said wide ly spaced end portions of said arcrunners of said first arc chamber to a position between said closelyspaced end portions of said electrodes in said second arc chamber.

2. A multi-stage electric circuit interrupter as set forth in claim 1wherein said first arc chamber includes a series of arc venting openingsdisposeed along a line extending between said widely spaced end portionsof said are runners, whereby most of the arc gases generated in saidfirst arc chamber are discharged through said openings, and a smallportion thereof are diverted to said second arc chamber to initiatebreakdown of the air space between said electrodes in said second arcchamber.

3. A multi-stage electric circuit interrupter is set forth in claim 2wherein said means connecting said electrodes of said second arc chamberto said arc runners of said first arc chamber include an electricalresistance device.

4. A multi-stage electric circuit interrupter as set forth in claim 3wherein said resistance means comprises a high positive temperaturecoefiicient of resistance type material.

5. A multi-stage electric circuit interrupter as set forth in claim 1wherein said circuit breaker also includes a third are chambercontaining a pair of spaced electrodes having closely spaced portionsand widely spaced portions, means electrically connecting said arcrunners of said third chamber electrically in parallel with said arerunners of said second arc chamber, and ionized-gas conduit meansextending from said second arc chamber at a point adjacent said widelyspaced portions of said runners of said second arc chamber to a pointadjacent said closely spaced portions of said are runners of said thirdarc chamber.

6. An electric circuit interrupter as set forth in claim 5 wherein saidconnections between said electrodes of said third enclosure and saidelectrodes of said second arc chamber include electrical resistancemeans.

' 7. An electric circuit interrupter as set forth in claim 6 whereinsaid resistance means comprise high positive temperature coefiicient ofresistance materials.

8. An electric circuit interrupter as set forth in claim 1 wherein saidinterconnecting means for said ionized gases comprises conduit meanshaving a portion thereof extending in the same direction as the vents ofsaid first enclosure and a second portion extending at an angle to saidfirst portion.

9. An electric circuit interrupter as set forth in claim 1, said circuitbreaker comprising a plurality of substantially identical generallyrectangular insulating casing portions, each of said are chambers beingcontained in a different one of said casing portions.

References Cited UNITED STATES PATENTS 1,819,207 8/1931 Slepion 200-1442,508,954 5/1950 Latour et a1. 313306 X 2,900,566 8/1959 Fischer 315-363,093,766 6/1963 Cobine 313-306 X 3,430,016 2/1969 Hurtle 31711 XFOREIGN PATENTS 25,287 12/ 1905 Great Britain. 991,926 5/1965 GreatBritain. 199,715 12/1965 Sweden.

ROBERT S. MACON, Primary Examiner R. A. VANDERHYE, Assistant ExaminerU.S. Cl. X.R. 200-445, 147, 168

